A phase II study of ixabepilone (BMS 247550) in metastatic renal cell carcinoma

14646 Introduction Ixabepilone (BMS) is a semi-synthetic analog of Epothilone B that functions as a microtubule stabilizer and has anti-cancer effects in several cancers including renal cell carcinoma (RCC) (Zhuang, ASCO 2004). The initial phase II study in RCC utilized a difficult and unconventional dosing schedule (6 mg/m2 IV days 1–5 every 21 days). Hence, this phase II study in RCC was designed to verify previous observations and to test the safety, feasibility, and activity of administering BMS once every 3 weeks- a schedule used in other malignancies. Methods Treatment consists of BMS 40 mg/m2 IV on day 1 every 3 weeks. Eligibility included metastatic RCC with clear or non-clear cell histology, no limits on the number of previous treatments, performance status 0–2, and normal organ function. The primary endpoint is the overall response rate by RECIST criteria on radiologic evaluation conducted every 9 weeks. Accrual to the full planned 41 patients (pts) will proceed provided that 2 or more responses are observed in the first 21 pts. Results Ten pts have enrolled (4 clear cell) with 1 declining participation prior to receiving any treatment. Eight pts have completed at least 3 cycles. Grade 3–4 toxicities include lymphopenia-2, diarrhea-2, alopecia-1, and infection-1. Grade 1–2 toxicities seen in more than 50% of pts include alopecia, neuropathy, nausea, fatigue, anemia, and lymphopenia. We have observed 1 unconfirmed partial response of short duration and 1 pt exhibited stable disease with a minor response but discontinued treatment due to excessive neurotoxicity. Three pts continue on treatment. Conclusions Toxicity at 40 mg/m2 IV on day 1 every 3 weeks is higher than previously reported with the daily x 5 schedule. While lymphopenia, diarrhea, neuropathy, and fatigue are all expected adverse events, the rates of toxicity across all grades is higher than previous reports. VHL mutation analysis is planned and will be correlated with response to therapy. Accrual and pt follow up continue. No significant financial relationships to disclose.